*{
    margin: 0;
    padding: 0;
}
a{
    color: #0070c9;
    text-decoration: none;
}
ul{
    list-style: none;
}
.auto{
    margin: 0 auto 0;   
}

.flex{
    display: flex;
}
html{
    overflow-x: hidden; /*表示水平方向隐藏溢出，没有滚动条*/
}